FTW03FA097

The catastrophic failure of the engine resulting from 1st stage turbine wheel blade failure due to type 1 hot corrosion (sulfidation). Contributing factors were the pilot's failure to brief the passengers on emergency safety equipment (life raft), the pilot's failure to deploy the skid-mounted emergency float system during the autorotation, the high wind conditions, and rough sea state.

The helicopter, flown by 19,000-hour pilot and transporting 4 passengers to an offshore oil platform, experienced a catastrophic engine failure and autorotated into open ocean water in the Gulf Of Mexico. Within a few seconds after landing on the water, the helicopter rolled inverted, the pilot and passengers exited, inflated their personal life vests, and waited for rescue. The pilot and one of the passengers drowned prior to rescue personnel arriving about 2 hours after the accident. Surviving passenger statements indicated that they were not aware of an emergency lift raft on-board the helicopter, and that the skid-mounted emergency float system was not inflated prior to landing. Rescue personnel reported high wind and rough seas in the area of the accident. Examination of the wreckage revealed that the float "ARM" switch was found in the disarmed position and its cover closed. The skid-mounted emergency floats were found inside their protective bags. The float system tested functional, and no anomalies were found during airframe component examinations. Download data from the ECU showed that engine performance prior to the loss of power was normal and the engine was operating in a steady state condition prior to the initial deterioration of NG. Detailed inspection of the engine revealed progressive turbine wheel damage throughout the power turbine. The damage varied from approximately 95% of the airfoil material missing on the 1st stage wheel to approximately 10% of the material missing on the 4th stage wheel. The damage observed in the gas producer turbine section was consistent with the separation of one or more of the first stage wheel airfoils. Mostly all of the fracture surfaces were obscured, typical of elevated turbine temperatures (according to the manufacturer, in excess of turbine and material limits). All 4 turbine wheels had evidence of solutioning and incipient melting was observed at the tips of the airfoil remnants. Fracture surfaces of the 1st stage wheel airfoils did not reveal the presence of fatigue. Detailed metallurgical examination revealed the presence of sulfides on the 1st and 2nd stage turbine wheel surfaces. According to the manufacturer, the presence of sulfides is evidence that sulfidation has occurred. Damage on the concave surface adjacent to the fractures near the leading edges of the airfoils was found consistent with type 1 hot corrosion (sulfidation) damage. Examination of radial cracks at the trailing edges of the airfoils revealed heavy oxidation consistent with thermal fatigue. According to Rolls Royce, that "thermal fatigue cracking at the airfoil base is not uncommon." Evidence of EPS 10649 (S1 Aluminide, which is a protective coating applied to the turbine wheel during manufacturing), was confirmed adjacent to the corrosive damage found on the wheels.

HISTORY OF FLIGHT On February 16, 2003, approximately 1225 central standard time, a Bell 407 single-engine helicopter, N407HH, registered to and operated by Houston Helicopters, Inc., of Pearland, Texas, executed an emergency landing into open ocean water in the Gulf of Mexico following a loss of engine power. The pilot and his four passengers survived the initial landing, however, the pilot and one passenger later drowned after egress from the helicopter. The remaining three passengers received serious injuries. Visual meteorological conditions prevailed, and a company visual flight rules (VFR) flight plan was filed for the Title 14 Code of federal Regulations Part 135 on-demand air taxi flight. Approximately 1210, the helicopter departed Harbor Island (TeSoro Heliport), Ingleside, Texas, for a 26.1 nautical mile flight to offshore platform, Ensco Rig 84 (Matagorda 700 block offshore), with an estimated time of arrival of 1230. According to recorded communication records provided by the operator, the pilot of N407HH had transmitted a "Mayday" call, approximately 1225, citing an engine failure, and that he was going to land the helicopter on the water. Sounds similar to an "engine-out" audio tone were heard in the background of the Mayday call. Upon reception of the Mayday call, the Coast Guard stationed at Aransas Pass, Texas, and Corpus Christi, Texas, were notified, and an immediate search and rescue was initiated by the operator, the Coast Guard, private water vessels, and other helicopter operators. Two of the surviving passengers reported that they heard a loud "bang" at the time of the loss of engine power. The survivors also reported that the helicopter rolled inverted within a few seconds after the landing and began to submerge. They stated that the skid-mounted emergency float system were not inflated at the time of the landing. The pilot and passengers exited the helicopter, inflated their life vests, and awaited their rescue. Approximately 1425, the pilot and passengers were recovered by the Coast Guard. (See 'Survival Aspects' section for additional details). The operator, Coast Guard helicopter pilots, pilot's of other search helicopters, and two of the passengers reported the winds were from the north at 25-40 mph with 5-9 foot sea swells. PERSONNEL INFORMATION The 19,000-hour pilot-in-command, held a valid commercial pilot certificate, issued on May 25, 1964, with a rotorcraft-helicopter rating. The pilot also held a valid mechanic certificate, issued December 8, 1965, with airframe and power plant ratings. His most recent second class medical certificate was issued on June 12, 2002, with the limitation that he must have available glasses for near vision. On the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2) the operator reported the pilot's total flight time in all aircraft was 19,339 hours, of which, 19,299 hours were in rotorcraft. The pilot's total accumulated flight time in the Bell 407 was151 hours. A review of company flight and duty records revealed the pilot flew 168.9 hours, 263.9 hours (27.9 Bell 407), and 232.8 hours (89.9 Bell 407) in years 2000, 2001, and 2002, respectively. His most recent flight experience was 57 hours, 21 hours, and 3.5 hours in the past 90 days, 30 days, and 24 hours, respectively. The pilot was off duty from February 6-10, 2003. Flight and duty records for February 11-16 were not recovered from the helicopter and are presumed destroyed. According to the aircraft's (N407HH) maintenance log for February 11-14, 2003, the pilot flew 1.2 hours on February 11, 1.2 hours on February 12, and 2.5 hours on February 14. A review of company records revealed that the pilot satisfactory completed company training and the airman competency/proficiency testing requirements (FAA CFR Part 135.293 (a) (b) Part 299) to act as pilot-in-command (PIC) of Bell 407 helicopters on May 8, 2001. The pilot's most recent recurrent ground training records, dated March 20, 2002, certified the pilot-in-command had received ground training on life rafts, survival vests, ditching procedures, and water survival techniques. Underwater egress training for the pilot could not be verified. The pilot's most recent competency/proficiency check, conducted by the company check airman, for the Bell 407 helicopter was satisfactorily performed on May 31, 2002. AIRCRAFT INFORMATION The Bell 407 helicopter, serial number (SIN) 53460, helicopter was manufactured in 2000, and issued an airworthiness certificate on December 9, 2000, and was registered to Houston Helicopters, Inc., on February 1, 2001. Total airframe time at the time of the accident was approximately 612.7 hours since manufactured. The helicopter was equipped with a Full Authority Digital Electronic Control system (FADEC) and Electronic Control Unit (ECU) with version 7102 software, which includes incident recording capability. On December 12, 2002, the last annual inspection of N407HH, which was accomplished at a total time of 546.8 hours by the Houston Helicopter, Inc., FAA certificated repair station, encompassed the 50 hour, 100 hour and 300 hour airframe inspection and the 150 hour engine inspection. During the inspection, the electrical system functional test, inflation test, and float pneumatic system checks and bottle servicing were satisfactorily performed for the emergency float system. The helicopter was not equipped with a cockpit voice recorder (CVR) or a digital flight data recorder (DFDR). The helicopter's power plant, installed new on October 28, 2000, was an 650-horsepower Allison/Rolls Royce 250-C47B turbo shaft engine, part number (PIN) 23063392, SIN CAE 847499. The last annual inspection engine inspection coincided with the last airframe inspection on December 12, 2002, at a total time of 546.8 hours. The turbine engine maintenance inspection was performed in accordance with the Rolls Royce/Allison Operations and Maintenance Manual. Total engine time at the time of the accident was 612.7 hours ( power cycles:1,679, start cycles:1,116). In May 2001, the operator found (during an inspection) that the internal engine oil filter was not installed. The time on the engine was 97.0 hours. On September 7, 2001, two bearings (258.6 hours) PIN 407-340-339-103, SIN C00-2514 and D00-0027 were removed and replaced. The starter generator (164.7 hours) was removed and replaced on July 3, 2002. Maintenance records for January 4, 2003, stated the "floats circuit breaker pops when float switch armed/repaired wire." Time on the aircraft was 562.4 hours. The last refueling of N407HH prior to the accident occurred on February 14, 2003, with a total of 90.2 gallons. WRECKAGE AND IMPACT INFORMATION Recovery On February 26, 2003, search for the submerged helicopter was initiated by the insurance company. Side scan sonar located the helicopter on February 27, 2003, at North 27 degrees 51 minutes 23.617 seconds; West 096 degrees 41 minutes 36.493 seconds (approximately 1,400 feet northeast of the last known position). According to divers, the helicopter was found inverted at a depth of 96 feet with 2 of the 4 main rotor blades embedded in sand and silt. The helicopter was raised on March 16, 2003. According to an FAA inspector, who was aboard the recovery vessel, the boat stabilizing pylon was inadvertently jacked down onto the wreckage, resulting crushing damage to the airframe and cabin. After the wreckage was raised, it was rinsed with fresh water on board the recovery vessel. The ECU and three instrument panel-mounted engine instruments (MGT, Torque, and Ng) were removed and placed in fresh water for preservation. The helicopter was brought to shore and transported via ground vehicle by Air Salvage of Dallas (ASOD), Lancaster, Texas, to the ASOD facility where is was secured for further examination by the Board. Initial Wreckage Examination Under the supervision of the NTSB IIC, the